std::swap_ranges

If any of the following conditions is satisfied, the behavior is undefined:

• The two ranges overlap.
• There exists a pair of corresponding iterators iter1 and iter2 in the two ranges such that *iter1 is not Swappable with *iter2.

[edit] Parameters

[edit] Return value

Iterator to the element past the last element exchanged in the range beginning with first2.

[edit] Complexity

Exactly std::distance (first1, last1) swaps.

[edit] Exceptions

The overload with a template parameter named ExecutionPolicy reports errors as follows:

• If execution of a function invoked as part of the algorithm throws an exception and ExecutionPolicy is one of the standard policies, std::terminate is called. For any other ExecutionPolicy, the behavior is implementation-defined.
• If the algorithm fails to allocate memory, std::bad_alloc is thrown.

[edit] Notes

Implementations (e.g. MSVC STL) may enable vectorization when the iterator type satisfies LegacyContiguousIterator and swapping its value type calls neither non-trivial special member function nor ADL-found swap.

[edit] Possible implementation

template<class ForwardIt1, class ForwardIt2>
constexpr //< since C++20
ForwardIt2 swap_ranges(ForwardIt1 first1, ForwardIt1 last1, ForwardIt2 first2)
{
 for (; first1 != last1; ++first1, ++first2)
 std::iter_swap (first1, first2);
 
 return first2;
}

[edit] Example

#include <algorithm>
#include <iostream>
#include <list>
#include <vector>
 
auto print = [](auto comment, auto const& seq)
{
 std::cout << comment;
 for (const auto& e : seq)
 std::cout << e << ' ';
 std::cout << '\n';
};
 
int main()
{
 std::vector <char> v{'a', 'b', 'c', 'd', 'e'};
 std::list <char> l{'1', '2', '3', '4', '5'};
 
 print("Before swap_ranges:\n" "v: ", v);
 print("l: ", l);
 
 std::swap_ranges(v.begin(), v.begin() + 3, l.begin());
 
 print("After swap_ranges:\n" "v: ", v);
 print("l: ", l);
}

Before swap_ranges:
v: a b c d e
l: 1 2 3 4 5
After swap_ranges:
v: 1 2 3 d e
l: a b c 4 5

[edit] See also

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